> I said "warn about the use of non-builtin modules", not disallow
> their use. AFAIK, the purpose of the exercise is to reduce the
> number of non-builtin modules being loaded early on during
> Python startup.

The purpose of the exercise is to avoid, as much as possible, the
numerous issues that have already been encountered because of the
startup procedure relying on locale in various conditions for
initialization of the standard streams.

You are proposing that we commit a one-time fix to fix the current
situation. Recent history shows that similar problems will arise again,
and waste useful developer time for committing urgency fixes in order to
fix the build (not to mention that the symptoms are sometimes difficult
to diagnose, such as in this very issue). I am proposing a broader
change which prevents, as much as possible, similar problems from
reappearing and will relieve us from a dispensable burden.

> > (note, this is already done elsewhere, for example _abcoll.py or
> > _weakrefset.py)
> 
> Those are special cases since they are needed for ABCs. locale
> is not special enough to warrant such a disruption in module
> organization and it's not needed either (see above).

"special enough" is in the eye of the beholder.